Derivative Instruments and Hedging Activities - Fair Value Hedge (Detail) (Other income (expense) [Member], Fair Value Hedging [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Swap [Member]
Derivatives And Hedging Activities [Line Items]
Gain/(Loss) on the hedged fixed rate debt attributable to changes in the market interest rates	$ (1,051)	$ (577)	$ (2,160)	$ (1,732)
Borrowings [Member]
Derivatives And Hedging Activities [Line Items]
Gain/(Loss) on the hedged fixed rate debt attributable to changes in the market interest rates	$ 1,051	$ 577	$ 2,160	$ 1,732